Studies of the transcription reactions involved in RNA chain initiation, RNA chain elongation and RNA chain termination have shown that these steps are regulated in all cells, and play an important role in regulation of gene expression. Recently, interest in these transcriptional steps has been increased by the finding of important regulatory effects that affect human genetic and infectious diseases, and that target initiation, elongation and termination. Examples include: expression of human protooncogenes, expression of the HIV virus and the interaction of the product of the von Hippel-Lindau tumor suppressor gene with the elongation factor Elongin. These findings have increased interest in the biochemical mechanisms of each of the 3 transcription steps listed above. We propose to continue our studies on these transcription steps as carried out by E. coli RNA polymerase by studying: (i) the relationship between RNA polymerase inchworming and the efficiency of rho independent termination, (ii) the position of RNA binding sites during transcript elongation along a transcription unit, (iii) the structure and sequence of RNAs that bind tightly in binary complexes with RNA polymerase, (iv) the mechanism of action of the lambda N antitermination factor, (v) the possible existence of complexes of protein factors with RNA polymerase holoenzyme and elongating RNA polymerase, (vi) the role of sequences in different parts of the promoter on the rate of promoter escape, and on the yield, sizes and pattern of formation of abortive transcripts in the RNA chain initiation reaction.